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Fthe rise to a depth of: 8.0 ft minus 0.67 ft rise of mound = 7.33 ft below grade. For ment (destruction of bacteria and viruses)to occur, the distance effluent should travel d conditions through the soil environment is generally regarded to be 5 feet. e and Hantzsche paper, they discuss three options to consider as potential methods of reducing the mounding phenomenon. The first is increasing the size of the disposal field. Based upon the average daily flow calculations found on Page 12, it is anticipated that the disposal area is sufficient in size to accommodate the projected flow volumes after complete build-out. The disposal area is based on mathematical computations for sizing found in the S.J.C. Sewage Standards and EHD parameters. The second method is elongating the shape of the area covered by the field. As noted on the design plans, the filter bed is elongated in a 3.3:1 length-to-width ratio. Additionally,the long axis of the filter bed is oriented toward the northeast. This orientation is perpendicular to the groundwater flow direction as observed in the on-site monitoring wells. Discussions in the scientific literature suggest that rectangular disposal area orientations perpendicular to groundwater flow may reduce the propensity for mound formation. Thirdly, operating the field intermittently should decrease the mounding effect. As noted in the filter bed design, there are two separate filter bed disposal areas. Effluent will be pumped by two separate pumps that will alternate between the two filter beds, thus creating intermittent dosing of each bed. If it is determined at some point in the future, that mounding effects are preventing proper effluent treatment and disposal, the area designated as the 100%replacement area may have to be activated. This reserve area is located northwest of the primary disposal area. This may occur prior to attaining the projected 2,180 gpd effluent flow volumes after the phased completion and full occupancy, but can be considered unlikely. E. URFACE WATER INFORMATION The surface water retention pond for the existing an ure development of the project will be at the southern end of the project, as denoted on t "bite Plans. There should be no un oundment water from the proposed filter bed due to a separation distance of approximately 150-200 fee Depending on the directional flow upper groundwater aquifers, the retention pon is cit er upgradient or crossgradient to the future filter bed. Regardless of groundwater directional flow,percolating rainwater from the basin into the top aquifer mixing layer may create a dilution effect to the percolating septic system effluent. However, this can only be truly discerned with complicated groundwater monitoring and modeling. According to a scientific paper authored by Shaw and Turyk(1994), reduction of nitrate concentrations in groundwater can occur primarily through dispersion, or by percolating rainwater recharge. Climatic Data: Rainfall rsus Evapotranspiration NLSP3.2� It i, enerallyrd scientifically accepted that when precipitation exceeds evapotrans- piration (Eto), deep percolation of surface rainwater impoundment may occur. Evapotranspiration refers to water evaporation that takes place both at the soil surface and transpiration by plants, and is defined as water loss from a large field of 4-to-7 inch tall, cool-season grass that is not water stressed. 9 Chesney Consulting